The present invention relates generally to semiconductor device packages, and more particularly to a lead frame design for quad flat no-lead (QFN) packages.
Semiconductor devices are widely used today. As these devices become smaller and more functional, it is desirable to have device packages that can accommodate larger dies with enhanced functionality.
One way of packaging the semiconductor dies involves the use of a lead frame that has a die pad on which one or more dies are mounted. The lead frame also includes electrical leads that project outwardly from the package and are used to allow electrical signals to be received by and transmitted from the one or more dies to a printed circuit board (PCB), or other external devices.
Another type of lead frame based package is a leadless package, such as dual flat no-lead (DFN) and quad flat no-lead (QFN) packages. In such packages, the leads do not project outwardly from the package but instead are flush with either the sides or bottom of the package, or both.
FIG. 1 is a cross-sectional view of a conventional leadless semiconductor package 10 having a semiconductor die 12, a lead frame 14 having a die flag 16 and lead fingers 18 surrounding the die flag 16. Bond pads of the semiconductor die 12 are electrically coupled to the lead fingers 18 with bond wires 20. A molding compound 22 encapsulates the semiconductor die 12 and the bond wires 20 to form the semiconductor package 10.
However, as can be seen, the size of the semiconductor die 12 that can be incorporated in the package 10 is limited by the size of the die flag 16 of the lead frame 14. Therefore, larger lead frames may be required to package large semiconductor dies thereby resulting in size, design and cost penalties. Moreover, use of larger lead frames may lead to additional customization requirements as smaller dimensioned interconnect configurations cannot be used.
Therefore a need exists for semiconductor packaging techniques that facilitate packaging of large semiconductor dies without increasing the overall package size.